Production of microfluid devices for performing biological and chemical screening with a small amount of liquid usually requires expensive semiconductor manufacturing equipment and also requires cumbersome operation and external devices such as a pump. Therefore, practical application of these devices is hampered by problems with costs, durability, and ease of use. In contrast, lateral flow or flow-through paper assay devices are produced by using porous media, and these devices determine the presence or absence of the target substance according to the movement of the substance in the porous medium due to capillary phenomenon; thus, these devices do not require cumbersome operation or external devices such as a pump, and therefore the above drawbacks can be overcome. Accordingly, these devices are attracting attention as enabling point-of-care testing (POCT) during medical diagnosis, and in environments requiring cost reduction, such as in developing countries.
Devices disclosed thus far include a sharp and highly sensitive lateral flow assay (Patent Document 1) in which a control line for preventing diffusion of a solution containing a biomaterial is formed in advance from a casein solution or the like, thereby preventing bleeding on the chromatographic strip, a method of sensitizing color development in immunochromatographic analysis using resonance plasmon effects between the labeled substances such as antibodies (Patent Document 2), a method of forming a fluid-impervious barrier inside a porous hydrophilic medium using polymerization photoresist or a curable polymer, thereby providing a complicated flow path pattern and reaction (Patent Document 3), and a dipstick method in which a solution is developed into multiple flow paths arranged in parallel (Patent Document 4).